android x86 doesn't define ffs in libc, use compiler builtin instead

Change-Id: Ifde1184e469fc9a74de007a0caf27750b2ffbcbb

external/cairo/cairo/cairo-1.10.2.android.patch

@@ -11,3 +11,14 @@
  	# Parse the version information argument.
  	save_ifs="$IFS"; IFS=':'
  	set dummy $vinfo 0 0 0
+diff -ur cairo.org/src/cairo-compiler-private.h cairo/src/cairo-compiler-private.h
+--- a/cairo.org/src/cairo-compiler-private.h	2016-01-16 00:47:17.392420675 +0100
++++ b/cairo/src/cairo-compiler-private.h	2016-01-16 00:51:55.601110129 +0100
+@@ -258,4 +258,7 @@
+ #define inline __inline__
+ #endif
+ 
++/* no ffs in libc on android x86 (at least not in v15 that we compile against) */
++#define ffs __builtin_ffs
++
+ #endif